An apparatus for aseptic processing of a viscous food product includes a product tank configured to hold the viscous food product. A first pump is configured to pump the viscous food product from the product tank through a heat exchanger at a given rate. A cleaning station including a cleaning pump configured to pump a flushing fluid through the product tank. A second pump is configured to pump a flushing fluid through the heat exchanger at the same rate as the first pump, while the cleaning pump is pumping the flushing fluid through the product tank and first pump.